The present invention relates to a public telephone set.
Since public telephone sets are installed and available in shops and on streets and can be used by all people, these telephone sets are often vandalized. In particular, a handset incorporating transmitting and receiving lines is connected to a telephone set housing through a cord of transmitting and receiving lines. An operation failure occurs due to a disconnection of the cord. In this case, no means for detecting such a disconnection is provided in a maintenance center. Therefore, although the handset is disconnected from the telephone set housing, the telephone set is left out of order until a third party calls the maintenance center or a periodic inspection of the public telephone set is performed. In a recent public telephone system, a self-diagnosis function is provided to determine whether a telephone circuit is normally operated, and a diagnostic result is acknowledged to a remote area, e.g., a maintenance center. However, no consideration is taken for a handset disconnection in this system. A typical example of the system is European Pat. No. 12,102 wherein a self diagnosis is performed when an off-hook signal is generated.